The present invention relates to a video measuring system and, more particularly, to a fast, efficient, user-friendly video measuring system.
It is known to employ a solid state TV camera for industrial process control. For example, U.S. Pat. No. 4,135,204 to Ray E. Davis, Jr. et al, which is entitled "Automatic Glass Blowing Apparatus And Method" and is assigned to the assignee of the present application, discloses the use of an analog video signal to control the growth of a thermometer end opening blister in a heated hollow glass rod by monitoring and iteratively controlling the growth of the edges of the blister using analog edge detection techniques. It is also known to employ a solid state TV camera in a video inspection system. For example, U.S. Pat. No. 4,344,146 to Ray E. Davis, Jr. et al, which is entitled "Video Inspection System" and is assigned to the assignee of the present application, discloses the use of such a TV camera in a high speed, real time video inspection system wherein the TV camera has at least sixteen levels of grey scale resolution.
The present invention represents an improvement over both of these prior art systems and complements the video inspection system of U.S. Pat. No. 4,344,146. In addition to being user-friendly, the present invention is highly efficient because it can effectively perform measurements using only a small part of the information obtained by the system. It is extremely fast while, at the same time, being relatively inexpensive and very reliable.
In a preferred embodiment, the present invention employs a pair of solid state TV cameras, a pair of interface/memory circuits (also known as "frame grabbers"), a pair of TV monitors, a computer, a keyboard, a joystick and strobe lights. In the system are stored a series of "menus" which guide the operator in defining those features of the object which are to be measured. These menus and the manner in which they are presented render the system very user-friendly.
Initially, the operator takes a picture of an object such as a package using the TV camera. The picture is stored in memory and displayed on the monitor. The operator then uses the joystick to manipulate a cursor on the monitor and specifies those features of the object to be measured. The operator designates points where the system is to start searching for the features and also specifies intensity gradient threshholds for the features. The intensity gradient is the rate of change of light intensity at a particular point on the monitor and has both a magnitude and a direction. It may be defined as the difference in intensity between neighboring picture elements.
If the object is a package having a closure and a label, the operator defines the package, defines the closure and defines the label. In addition, the operator specifies tolerances for these measurements. All of this is done with the assistance of various menus which are presented to the operator and provide step-by-step guidance for the operation of the system.
After this information has been entered and stored, the system is ready to operate. A picture is now taken of each package as it moves past the TV camera, for example along a high speed fill line. The picture is stored and the system measures the package, the closure and the label for each package. The system will indicate when these features are out of tolerance or missing altogether so that corrective action can be taken.
An important advantage of the present invention is that it permits accurate measurements but does not require large amounts of data to effect the measurements. Thus, to measure an object the system starts at specific points and searches along lines of picture elements or "pixels," looking for gradients which exceed the selected threshholds. It is not necessary for the system to examine more than a small percentage of the pixels in order to measure an object or a particular feature of the object. For example, if the TV camera comprises a two dimensional array containing over 50,000 photodetectors, it is possible to measure an object by examining fewer than 400 pixels, or less than one percent of the information captured and presented on the TV monitor. Similarly, it is possible to measure a series of features using less than five percent of the pixels.
Because the video measuring system is user-friendly, and because it is highly efficient in its use of information, it is an extremely valuable industrial tool. Thus, it can be used for process control in manufacturing operations, for the quality control of both raw materials and finished goods, and to provide sensory signals for robotics.